#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
int main() {
	int a; float b=0;
	for (a = 1; a < 101; a++)
	{
		if (a % 2 == 1)b = b + (float)1 / a;
		else b = b - (float)1 / a;
	}
	printf("%f", b);
}













